This invention relates to a method and apparatus for operating a non-volatile memory system for use in an intelligent terminal.
There are certain problems which exist with terminals of the type which are used for financial or banking purposes, hotel/motel reservations, retailing, and the like. Continuous efforts are being made to reduce the costs of manufacturing, maintaining, and operating these terminals.
One of the problems which exists with these prior art terminals is that they frequently use Programmable Read Only Memories or PROMs to store their associated application programs; this makes the storage costs expensive. Also, changes in the programs cannot be readily made in the field or at a customer's site; this necessitates changes to be made at the factory, thereby resulting in a significant delay to the customer.
Another problem which exists with terminals which use Read Only Memories or ROMs is that while they provide inexpensive storage, their use does not permit changes or updates to be made in the field. When changes are necessary, they are effected by the ROM vendor. This means that long delays may eventuate. If many or frequent changes are required, the cost advantage for using ROMs is lost.
Those terminals which use dynamic RAMs have the advantage of "ease of effecting a change in the field" compared to terminals which use ROMs and/or PROMs in their memory systems. However, the use of dynamic RAMs requires "refresh logic" and a battery back-up system to provide for non-volatility of the application programs stored therein. The non-volatility achieved by this technique exists for only a short time, especially for a memory system which is large enough to store application programs. Also, the use of dynamic RAMs requires a cassette, floppy disc or a hard disc device for permanent storage of the application programs and for daily loading of the programs into the dynamic RAMs.
The prior art terminals previously described may also require a permanent battery back-up for some data such as totals and constants which may need to be changed during normal operation of the terminal.